The Hague court has suspended an appeals hearing after the Bosnian Croat wartime commander Slobodan Praljak claimed to had drunk poison.
Praljak was one of six former Bosnian Croat political and military leaders who were appealing their sentences in The Hague.
The 72-year-old tilted back his head and took a swing from a small flask or glass as the judge read out that his 20-year prison sentence had been upheld.
“I am not a war criminal, I oppose this conviction,” he said after drinking. The presiding judge called for a doctor and halted the proceedings.
The Bosnian Croat wartime commander died a few hours later.
Praljak was originally sentenced in 2013 for his involvement in a campaign to drive Muslims out of a would-be Bosnian Croat mini-state in Bosnia in the early 1990s.
Presiding Judge Carmel Agius had overturned some of Praljak’s convictions but left his sentence unchanged.
Wednesday’s hearing was the final case at the groundbreaking tribunal before it closes its doors next month.
The tribunal, which last week convicted former Bosnian Serb military chief General Ratko Mladic of genocide and other crimes, was set up in 1993, while fighting still raged in the former Yugoslavia.
It indicted 161 suspects and convicted 90 of them.
The appeals judges upheld a key finding that late Croat president Franjo Tudjman was a member of a plan to create a Croat mini-state in Bosnia.
Two other suspects had also had their sentences upheld before the hearing was halted.